Date : Thu, 07 Apr 1983 05:01:00 EST
From : Keith Petersen <W8SDZ@mit-mc.arpa>
Subject: Hard disk floppy interface
AS-100 Virtual Floppy Disk
Controller for 5.25 inch Winchesters
April, 1983
The AS-100 is the only Winchester disk controller that connect
directly to your existing floppy disk controller. The AS-100
interfaces to the host as one or two floppy disk drives.
* The host interface is totally compatible with the Shugart
Associates SA850 and SA450 floppy disk drive interfaces,
permitting simple connection to virtually any floppy-based
computer system.
* An on-board microcomputer permits buffered seek. Step rates
of up to 2500 steps per second are supported.
* Automatic read-after-write check by the AS-100 ensures data
reliability.
* The AS-100 dissipates only 5 watts for cool operation and
low power supply drain.
* The floppy track format is soft-sectored and can be
formatted in any convenient single or double density format. All
the un-formatted track capacity of the Winchester is available to
the user.
CONFIGURATION
The AS-100 controller supports a single Winchester drive with
two, four or eight heads. The host interface can be configured
as one or two floppy disks, single or double sided.
Configuration is by jumper plugs and can be changed at any time
for any drive/host combination.
The host interface can be configured as either eight inch floppy
or minifloppy. If the eight inch configuration is selected, the
interface is exactly as defined by Shugart Associates as the
SA850. If the minifloppy interface is selected, the floppy data
rate is divided by two, however, the full track capacity of the
Winchester is still available (10,400 bytes).
There is no limitation within the AS-100 as to how many tracks
there may be, therefore, Winchesters of any capacity may be
supported. One popular configuration, using the Seagate
Technology ST-506 yields two double-sided floppies, each with
nine 1024 byte sectors per track and 153 cylinders for a total
capacity of 5.5 megabytes, formatted.
HOST INTERFACE
50 pin connector (SA850) 34 pin connector (SA450)
10 TWO-SIDED 6 DS4
14 SIDE SELECT 8 INDEX
20 INDEX 10 DS1
22 READY 12 DS2
26 DS1 14 DS3
28 DS2 18 DIRECTION
30 DS3 20 STEP
32 DS4 22 WRITE DATA*
34 DIRECTION 24 WRITE GATE
36 STEP 26 TRACK ZERO
38 WRITE DATA* 30 READ DATA
40 WRITE GATE 32 SIDE SELECT
42 TRACK ZERO
46 READ DATA
*NOTE: The AS-100 does not accommodate write data pre-
compensation. Write Data must be presented on-time. A minor
modification to your floppy controller may be necessary.
COMPATIBILITY
The AS-100 is compatible with the Seagate Technology family of
Winchester disk drives and with others which support the Seagate
interface. Among these are:
Tandon TM-600
RMS RMS-500
IMI
And many others.
SPECIFICATIONS
Electrical:
+5 volts @ 1.0 amps
+12 volts @ 0.1 amps
Physical:
Length: 11.0 inches
Width: 5.75 inches
Height: 0.5 inches
Weight: 0.6 pounds
SOFTWARE CONSIDERATIONS
The AS-100 has little software impact on most floppy-based
computer systems. The operating system must be told, however,
that 'these floppies are bigger' than the others. Using the CP/M
operating system, this is relatively simple. You merely change
and dedicate an existing disk parameter block to the Winchester
or create a unique table for the Winchester. For example, the
table below will define a single 5.5 megabyte Winchester:
DPB0: DW 144 ;SEC PER TRACK
DB 6 ;BLOCK SHIFT
DB 63 ;BLOCK MASK
DB 3 ;EXTNT MASK
DW 685 ;DISK SIZE-1
DW 511 ;DIRECTORY MAX
DB 192 ;ALLOC0
DB 0 ;ALLOC1
DW 0 ;CHECK SIZE
DW 2 ;OFFSET
ALV0: DS 86
CSV0: DS 0
For more information contact:
ALPHA SYSTEMS CORPORATION
711 Chatsworth Place
San Jose, California 95128
(408) 297-5583